There are anti-newtoning negative carriers for Focomat enlargers. They didn't come as a standard stock part, are kind of rare, but Glennview Cameras used to stock a ton of parts for Leitz enlargers. I don't even know whether they are still in business.
Check here:
http://www.glennview.com/leitz.htmPresumably you could get a piece of anti-newtoning glass cut to either replace the piece in your negative carrier or as an addition between the condenser and the film. I think the original carrier on the Focomat did have a single sheet of glass that held the negative flat, rather than the condenser surface itself???
J Ake :twisted: